Systems and methods for optically sensing characteristics of a blood flow

Abstract

Systems and methods for optically sensing characteristics of a blood flow provide a light source having a driver circuit that includes a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source. The systems and methods also include a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity. A receiver circuit including a bandpass filter is coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency.

1. An assembly for optically sensing characteristics of a blood flow comprising
 a light source, 
 a driver circuit for the light source including a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source, 
 a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity, and 
 a receiver circuit including a bandpass filter coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency. 
 
   
   
     2. An assembly according to  claim 1 
 wherein the selected carrier frequency is below the frequency components comprising electromagnetic interference. 
 
   
   
     3. An assembly according to  claim 1 
 wherein the selected carrier frequency is above the frequency components comprising ambient light. 
 
   
   
     4. A method for optically sensing characteristics of a blood flow comprising the steps of
 providing a light source having a driver circuit that includes a source of constant current and a modulator that modulates the constant current at a selected carrier frequency for transmission to the light source, 
 providing a light sensor for receiving light from the light source and producing a modulated output proportional to received light intensity, and 
 providing a receiver circuit including a bandpass filter coupled to the light sensor to receive the modulated output and having a center frequency at or near the selected carrier frequency to eliminate frequency components above and below the selected carrier frequency. 
 
   
   
     5. A method according to  claim 4 
 wherein the selected carrier frequency is below the frequency components comprising electromagnetic interference. 
 
   
   
     6. A method according to  claim 4 
 wherein the selected carrier frequency is above the frequency components comprising ambient light.